1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _ASM_ARCHRANDOM_H
3 #define _ASM_ARCHRANDOM_H
4 
5 #ifdef CONFIG_ARCH_RANDOM
6 
7 #include <linux/bug.h>
8 #include <linux/kernel.h>
9 #include <asm/cpufeature.h>
10 
11 static inline bool __arm64_rndr(unsigned long *v)
12 {
13 	bool ok;
14 
15 	/*
16 	 * Reads of RNDR set PSTATE.NZCV to 0b0000 on success,
17 	 * and set PSTATE.NZCV to 0b0100 otherwise.
18 	 */
19 	asm volatile(
20 		__mrs_s("%0", SYS_RNDR_EL0) "\n"
21 	"	cset %w1, ne\n"
22 	: "=r" (*v), "=r" (ok)
23 	:
24 	: "cc");
25 
26 	return ok;
27 }
28 
29 static inline bool __must_check arch_get_random_long(unsigned long *v)
30 {
31 	return false;
32 }
33 
34 static inline bool __must_check arch_get_random_int(unsigned int *v)
35 {
36 	return false;
37 }
38 
39 static inline bool __must_check arch_get_random_seed_long(unsigned long *v)
40 {
41 	/*
42 	 * Only support the generic interface after we have detected
43 	 * the system wide capability, avoiding complexity with the
44 	 * cpufeature code and with potential scheduling between CPUs
45 	 * with and without the feature.
46 	 */
47 	if (!cpus_have_const_cap(ARM64_HAS_RNG))
48 		return false;
49 
50 	return __arm64_rndr(v);
51 }
52 
53 
54 static inline bool __must_check arch_get_random_seed_int(unsigned int *v)
55 {
56 	unsigned long val;
57 	bool ok = arch_get_random_seed_long(&val);
58 
59 	*v = val;
60 	return ok;
61 }
62 
63 static inline bool __init __early_cpu_has_rndr(void)
64 {
65 	/* Open code as we run prior to the first call to cpufeature. */
66 	unsigned long ftr = read_sysreg_s(SYS_ID_AA64ISAR0_EL1);
67 	return (ftr >> ID_AA64ISAR0_RNDR_SHIFT) & 0xf;
68 }
69 
70 static inline bool __init __must_check
71 arch_get_random_seed_long_early(unsigned long *v)
72 {
73 	WARN_ON(system_state != SYSTEM_BOOTING);
74 
75 	if (!__early_cpu_has_rndr())
76 		return false;
77 
78 	return __arm64_rndr(v);
79 }
80 #define arch_get_random_seed_long_early arch_get_random_seed_long_early
81 
82 #else
83 
84 static inline bool __arm64_rndr(unsigned long *v) { return false; }
85 static inline bool __init __early_cpu_has_rndr(void) { return false; }
86 
87 #endif /* CONFIG_ARCH_RANDOM */
88 #endif /* _ASM_ARCHRANDOM_H */
89